<template>
	<view class="u-slider" @tap="onClick" :class="[disabled ? 'u-slider--disabled' : '']" :style="{
		backgroundColor: inactiveColor
	}">
		<view
			class="u-slider__gap"
			:style="[
				barStyle,
				{
					height: height + 'rpx',
					backgroundColor: activeColor
				}
			]"
		>
			<view class="u-slider__button-wrap" @touchstart="onTouchStart" 
				@touchmove="onTouchMove" @touchend="onTouchEnd" 
				@touchcancel="onTouchEnd">
				<slot v-if="$slots.default  || $slots.$default"/>
				<view v-else class="u-slider__button" :style="[blockStyle, {
					height: blockWidth + 'rpx',
					width: blockWidth + 'rpx',
					backgroundColor: blockColor
				}]"></view>
			</view>
		</view>
	</view>
</template>

<script>

export default {
	name: 'u-slider',
	props: {
		
		value: {
			type: [Number, String],
			default: 0
		},
		
		disabled: {
			type: Boolean,
			default: false
		},
		
		blockWidth: {
			type: [Number, String],
			default: 30
		},
		
		min: {
			type: [Number, String],
			default: 0
		},
		
		max: {
			type: [Number, String],
			default: 100
		},
		
		step: {
			type: [Number, String],
			default: 1
		},
		
		height: {
			type: [Number, String],
			default: 6
		},
		
		activeColor: {
			type: String,
			default: '#2979ff'
		},
		
		inactiveColor: {
			type: String,
			default: '#c0c4cc'
		},
		
		blockColor: {
			type: String,
			default: '#ffffff'
		},
		
		blockStyle: {
			type: Object,
			default() {
				return {};
			}
		},
	},
	data() {
		return {
			startX: 0,
			status: 'end',
			newValue: 0,
			distanceX: 0,
			startValue: 0,
			barStyle: {},
			sliderRect: {
				left: 0,
				width: 0
			}
		};
	},
	watch: {
		value(n) {
			
			if(this.status == 'end') this.updateValue(this.value, false);
		}
	},
	created() {
		this.updateValue(this.value, false);
	},
	mounted() {
		
		this.$uGetRect('.u-slider').then(rect => {
			this.sliderRect = rect;
		});
	},
	methods: {
		onTouchStart(event) {
			if (this.disabled) return;
			this.startX = 0;
			
			let touches = event.touches[0];
			
			this.startX = touches.clientX;
			
			this.startValue = this.format(this.value);
			
			this.status = 'start';
		},
		onTouchMove(event) {
			if (this.disabled) return;
			
			
			if (this.status == 'start') this.$emit('start');
			let touches = event.touches[0];
			
			this.distanceX = touches.clientX - this.sliderRect.left;
			
			
			this.newValue = (this.distanceX / this.sliderRect.width) * 100;
			this.status = 'moving';
			
			this.$emit('moving');
			this.updateValue(this.newValue, true);
		},
		onTouchEnd() {
			if (this.disabled) return;
			if (this.status === 'moving') {
				this.updateValue(this.newValue, false);
				this.$emit('end');
			}
			this.status = 'end';
		},
		updateValue(value, drag) {
			
			const width = this.format(value);
			
			if(width > this.max || width > 100) return;
			
			let barStyle = {
				width: width + '%'
			};
			
			if (drag == true) {
				barStyle.transition = 'none';
			} else {
				
				delete barStyle.transition;
			}
			
			this.$emit('input', width);
			this.barStyle = barStyle;
		},
		format(value) {
			
			return Math.round(Math.max(this.min, Math.min(value, this.max)) / this.step) * this.step;
		},
		onClick(event) {
			if (this.disabled) return;
			
			const value = ((event.detail.x - this.sliderRect.left) / this.sliderRect.width) * 100;
			this.updateValue(value, false);
		}
	}
};
</script>

<style lang="scss" scoped>
@import "../../libs/css/style.components.scss";

.u-slider {
	position: relative;
	border-radius: 999px;
	border-radius: 999px;
	background-color: #ebedf0;
}

.u-slider:before {
	position: absolute;
	right: 0;
	left: 0;
	content: '';
	top: -8px;
	bottom: -8px;
	z-index: -1;
}

.u-slider__gap {
	position: relative;
	border-radius: inherit;
	transition: width 0.2s;
	transition: width 0.2s;
	background-color: #1989fa;
}

.u-slider__button {
	width: 24px;
	height: 24px;
	border-radius: 50%;
	box-shadow: 0 1px 2px rgba(0, 0, 0, 0.5);
	background-color: #fff;
	cursor: pointer;
}

.u-slider__button-wrap {
	position: absolute;
	top: 50%;
	right: 0;
	transform: translate3d(50%, -50%, 0);
}

.u-slider--disabled {
	opacity: 0.5;
}
</style>
